In the prior art, there is a blind area about overvoltage protection, that is, at the moment of power on, the module input overvoltage protection is performed by the protection circuit of the module in normal work state. In this way, there exists a problem of the delayed protection. Therefore, the power supply module may have a possibility of breaking down or may break down immediately. In addition, a second auxiliary power supply board is required to identify and determine the input voltage after the power supply module is disconnected, so as to re-connect the power supply module to the system after the voltage of the power network is lowered. However, this leads to increased costs and decreased reliability